Adding timer for transfering the metadata on GPU.

src/problems/tnlHeatEquationProblem.h

src/problems/tnlHeatEquationProblem_impl.h

src/problems/tnlPDEProblem.h

src/problems/tnlPDEProblem_impl.h

src/solvers/pde/tnlExplicitUpdater.h

src/solvers/pde/tnlExplicitUpdater_impl.h

src/solvers/pde/tnlPDESolver_impl.h

tests/benchmarks/tnl-benchmark-simple-heat-equation.h